This invention relates to rollers which support reel mower cutting units above the ground.
Reel mower cutting units of conventional design include a cylindrical cutting reel having a plurality of cutting blades extending in spiral or helical patterns around the reel's axis of rotation. These cutting blades rotate in close proximity to a laterally extending bed knife for cutting vegetation with a shearing action. Reel mower cutting units include a frame within which the cutting reel and bedknife are supported. Conventional reel mower cutting units include front and rear rollers which roll in contact with the ground for supporting the cutting unit during operation. The rollers are vertically adjustable for establishing the height at which vegetation is cut by the reel and bedknife. This type of conventional reel mower provides a very accurate and precise cutting of grass. Reel mowers are therefore typically used in highly manicured areas where precision turf mowing is necessary, such as golf courses.
Many such conventional cutting units provide rollers having a cylindrical shape and a smooth continuous surface. The smooth outer surface of the roller rolls in contact with the ground during mowing operations. As the roller encounters debris such as clumps of grass, sand or dirt, the roller will rise up to ride over the obstruction, thereby affecting the height at which grass is cut. Even small obstructions or debris which lie in the path of the smooth rollers tends to negatively affect the cut quality. Furthermore, debris such as grass clippings, sand or dirt tends to accumulate on the outer surface of the smooth roller, which increases the effective diameter of the smooth roller. This causes the reel and bedknife to ride higher above the ground, thereby altering the cutting height. It is known to provide roller scrapers which wipe or scrape the debris from the surface of the smooth roller. These roller scraper mechanisms add cost, complexity and weight to the cutting unit. Furthermore, the roller scrapers are positioned in a crowded or cramped space within the cutting unit frame between the roller and cutting reel. Therefore, to provide room for the roller scraper the roller must be sufficiently spaced from the cutting reel. When the roller is spaced a large distance from the cutting reel the cutting unit has a larger effective wheel base and the reel and bedknife positioned between the rollers are less able to accurately follow small undulations in the ground contour. Cut quality is thereby negatively affected. This type of smooth surfaced roller has the further disadvantage of pressing down the grass to be mowed, which negatively affects cut quality.
A second type of cutting unit roller is the grooved roller. Grooved rollers provide a tube on which a plurality of washers and spacers are stacked. The spacers are positioned between adjacent washers to provide a space or groove therebetween. The washers have a larger diameter than the spacers, and therefore the outer radial edge of the washers contacts the ground surface during operation. The washers rolling in contact with the turf to be mowed cause some blades of grass to stand upright or erect, which makes it easier for the cutting reel to cut the grass and thereby helps improve cut quality. The washers are typically not manufactured to a high tolerance, so the washers may have somewhat different effective diameters. This may result in the roller having a non-uniform diameter which might cause the cutting unit to mow the grass at different heights as the cutting unit rolls across the ground. The low manufacturing tolerances of the various parts allows the grooved roller assembly to be manufactured relatively inexpensively, but cut quality can be negatively affected by the low manufacturing tolerances.
As the grooved roller encounters an obstruction such as a small clump of grass, dirt or sand, the obstruction can pass on either side of the washer and through the space provided by the spacer. Therefore, small obstructions or debris in the path of the roller do not significantly affect the cutting height when grooved rollers of this type are utilized. Furthermore, unlike smooth rollers, grooved rollers do not provide a large ground engaging surface on which debris can accumulate. The debris does not tend to accumulate on the outer edges of the washers which contact the ground during operation. Rather, the debris tends to accumulate in the space between adjacent washers, and on the vertical side surfaces of the washers. Minor accumulation of debris on the sides of the washers generally does not affect the cutting height or cut quality of the cutting unit. Nevertheless, grooved rollers have been provided with a scraper mechanism or comb apparatus which is biased against the grooved roller for scraping or wiping debris from between the washers. Debris is thereby prevented from accumulating between the washers to such a large extent that the roller's effective diameter is increased and cut quality is affected. The scrapers insure that the roller's effective diameter remains unchanged during operation. Comb type scrapers add cost, complexity and weight to the cutting unit.
Grooved rollers are typically coupled to the front of the cutting unit, and a smooth roller is typically coupled to the rear portion of the cutting unit. The smooth rear roller serves to smooth out or flatten the surface of the ground after the cutting unit has passed over it. However, the washers of the grooved roller tend to create impressions in the ground surface over which the grooved roller passes. The smooth roller at the rear of the cutting unit is typically incapable of smoothing out all traces of the impressions caused by the grooved roller. Conventional grooved rollers therefore may leave unsightly marks or indentations in a smooth ground surface such as a golf course green even when a smooth roller is provided at the rear of the cutting unit.
Soil compaction can hinder turf growth and is therefore a major concern of golf course superintendents. The many washers and spacers which must be positioned on the tube of a conventional grooved roller in order to span the entire width of the cutting unit add a relatively large amount of weight to the cutting unit. The heavy weight undesirably contributes to soil compaction beneath the cutting unit during operation.
Another type of roller is a machined grooved roller. Instead of having washers and spacers which are stacked on a tube, a machined grooved roller is manufactured by machining grooves in an otherwise generally solid roller. Vertically extending portions remain between the machined grooves. The vertically extending portions roll in contact with the ground much like the outer edges of the washers of a grooved roller having stacked washers and spacers. Machined grooved rollers have the advantage of being readily manufacturable with a very tight tolerance, which helps establish a uniform effective roller diameter. The uniform diameter allows the cutting unit to operate at a constant cutting height, which generally results in improved cut quality. However, the machining process is relatively expensive. Furthermore, machined grooved rollers are typically relatively heavy, and therefore negatively contribute to soil compaction.
It would therefore be desirable to provide a reel mower cutting unit with a roller that is light weight so that soil compaction is minimized. It would also be desirable for the roller to ride across small obstructions such as clumps of grass, dirt or sand without adversely affecting the height of cut or the cut quality. It would be desirable for such a roller to generally hinder or prevent the accumulation of this debris on the roller without requiring a heavy or bulky roller scraper.